t = 0 (slider from 0 to 20, step 0.1)
C: (0.5 * cos(-(t)), 0.5 * sin(-(t)))
A = Intersect(xAxis, yAxis)
c = Circle(A, C)
f(x) = 0.5 * sin(-(x))
g(x) = 0.5 * cos(-(x))
D: (t, 0.5 * sin(-(t)))
S: (t, 0.5 * cos(-(t)))